Cover Feature: EfficencyPallet jacks and sore backs
Programmable logic controllers, warehouse management software, automated guided vehicles and a new, raised conveyor system are all part of an efficiency-improving retrofit at a plant that produces ink...
April 1, 2000 | By MRO Magazine
Programmable logic controllers, warehouse management software, automated guided vehicles and a new, raised conveyor system are all part of an efficiency-improving retrofit at a plant that produces ink jet cartridges and components for home and office printers.
Bruce Johnson, project manager for Hewlett-Packard’s Ink Jet Business Unit explains the difference between his division’s previous material handling system and the current system.
Except for inventory control, the previous system was not designed for high volume manufacturing. Some of the manual processes were not as ergonomically sound as would be desired–“pallet jacks and sore backs,” as Johnson refers to it. As volumes increased, human error resulted in a lack of accuracy, and procedures became cumbersome to follow.
The company’s Ink Jet Business Unit (IJBU) is part of a 2-million-sq-ft facility located in Corvallis, Oregon. The IJBU designs, manufactures and markets supplies for use in inkjet printing devices.
Recognizing the need for a more efficient and accurate method of moving materials through the factory, IJBU acquired a highly sophisticated material handling system called ATLAS.
The system has had a dramatic impact on the division’s material handling capacity, throughput, and flexibility. While IJBU continues to assess the system’s benefits over time, estimates show an ability to double the current materials throughput without additional labour and cost.
The components comprising the ATLAS system–including programmable logic controllers, warehouse management software, and automated guided vehicles (AGVs), to name just a few–were provided by a wide spectrum of vendors. At the suggestion of the systems integrator, Hewlett-Packard chose Mathews Conveyor, a designer and manufacturer of material handling equipment with facilities in Port Hope, Ont., Danville, Kentucky and Mansfield, Ohio. Mathews provided IJBU with a 3,000-ft combination of pallet and case conveyors.
“This was not a simple case of having the conveyor go from point A to point B,” says Johnson. “We needed an ‘intelligent’ conveyor that would give us the capability to accumulate, sort and drop off items at numerous side spurs within the system.
“Using modular conveyors, we were able to construct an efficient conveyor system that could be adapted to our plant layout.”
Conveyor durability was also crucial, given the volume and weight of materials and finished goods that are processed each day. The case conveyor was designed to handle 50-lb loads. It is a line shaft conveyor rated at 40 lb/ft. The pallet conveyor is a chain-driven live roller, rated at 780 lb/ft to provide a load capacity of 3,000 lb per pallet.
Raw materials, thousand of pounds per day, arrive at Hewlett-Packard on hundreds of 40×48-in. wood pallets. The 600-ft Mathews pallet conveyor inducts these 56-in.-high pallets into the receiving area as they are off-loaded from delivery trucks. The data is stored in the Automated Storage and Retrieval System (AS/RS), which contains thousands of pallet locations.
“The pallet conveyor is a vital part of our operation,” Johnson emphasizes. “We require at least 98% uptime from the system; we need 99% or better from the conveyor.”
When a pallet of raw materials is required for production, specialized software schedules pallet retrievals from the AS/RS based upon a pull algorithm at the production lines. Loads travel on the pallet conveyor to the picking stations. Four manual picking P&D’s (pick and delivery) and two P&D’s at the auto-depalletizer robot cell–which does most of the picking–perform the picking process.
The management software instructs the robot or a material handler to pick the correct part number, quantity and type of parts to satisfy the pull request(s) from the production line. Most high-volume parts are forward-picked by whole pallet quantities at the auto-depalletizer into tote-based system storage, and then are sent one by one out to production via a line shaft case conveyor, which loops up into a 22-ft-high area above a drop ceiling. Four elevator-like lifts drop the totes of material down to floor level and hand them off to the AGVs that provide a flexible link to a variety of production line drop-off points.
A number of factors led to the decision to suspend the conveyor above the production floor. “One of the primary issues was space,” Johnson says. “The production area aisles are shared by personnel, pallet jacks, AGVs, and various other facility and production equipment. In addition, the aisles have multiple access points into the production lines, limiting the ability to install ground-level conveyors with straight runs of any significant length.
“Contamination due to particles, dust, and warehouse dirt were also undesirable in the production area,” he added. “By keeping the conveyor separated from the area below we avoid most problems of air-borne contamination from the totes, abrasion of cases on the conveyor rollers, and any other sources.”
Once completed, finished goods are collected from various production lines and packaging areas, sent back up the lifts, and conveyed overhead on the case conveyor into the distribution and shipping area, where they are automatically palletized by part number. They are loaded directly on to trucks for worldwide shipping.
Johnson has high praise for his division’s material handling system. “Your material-handling system is an extension of the production process,” he says. “With an efficient one, you can significantly impact your bottom line in a number of ways: time savings, accuracy and reduction of labour costs.
“Our material-handling system is the heart of our manufacturing support operations. We regard the conveyor as sort of the veins and arteries that tie it all together.”